U.S. patent application number 15/270607 was filed with the patent office on 2018-03-01 for multi-mode laser energy control for thermochromic print systems.
This patent application is currently assigned to Xerox Corporation. The applicant listed for this patent is Xerox Corporation. Invention is credited to Timothy M. Hunter.
Application Number | 20180063357 15/270607 |
Document ID | / |
Family ID | 61244065 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180063357 |
Kind Code |
A1 |
Hunter; Timothy M. |
March 1, 2018 |
MULTI-MODE LASER ENERGY CONTROL FOR THERMOCHROMIC PRINT SYSTEMS
Abstract
A printing system and method comprising a transport system
configured to move a print target, a laser for directing energy on
the print target, and a control system configured to adjust the
energy directed on the print target according to a present speed of
the print target the control system further comprising an analog
control, a scrolling window control, a pulse width modulation
control, and a halftone modulation control.
Inventors: |
Hunter; Timothy M.;
(Webster, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Xerox Corporation |
Norwalk |
CT |
US |
|
|
Assignee: |
Xerox Corporation
|
Family ID: |
61244065 |
Appl. No.: |
15/270607 |
Filed: |
September 20, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62382412 |
Sep 1, 2016 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N 1/0446 20130101;
H04N 1/036 20130101; H04N 1/40037 20130101; H04N 2201/0082
20130101; H04N 1/12 20130101; H04N 1/4056 20130101 |
International
Class: |
H04N 1/04 20060101
H04N001/04; H04N 1/12 20060101 H04N001/12; H04N 1/036 20060101
H04N001/036; H04N 1/405 20060101 H04N001/405 |
Claims
1. A printing system comprising: a transport system configured to
move a print target; a laser for directing energy on said print
target; and a control system configured to adjust said energy
directed on said print target according to a present speed of said
print target.
2. The system of claim 1 wherein said control system further
comprises: an analog control; a scrolling window control; a pulse
width modulation control; and a halftone modulation control.
3. The system of claim 2 wherein said control system implements
said analog control when said present speed of said target is in an
analog control speed range, said control system implements said
scrolling window control when said present speed of said target is
in a scrolling window control speed range, said control system
implements said pulse width control when said present speed of said
target is in a pulse width control speed window, and said control
system implements said halftone modulation control when said
present speed of said target is in a halftone modulation control
speed window.
4. The system of claim 3 wherein said analog control comprises:
providing an input current to a laser diode array wherein said
input current results in an output power of said laser diode that
has a substantially linear relationship to said input current.
5. The system of claim 3 wherein said scrolling window control
comprises: adjusting the exposure time said energy is directed on
said print target by adjusting a target window size associated with
said print target wherein said target window size corresponds with
said present speed when said present speed is in said scrolling
window control speed range.
6. The system of claim 3 wherein said pulse width modulation
control a comprises: adjusting an exposure time said energy is
directed onto said print target wherein said exposure time
corresponds with said present speed when said present speed is in
said pulse width control speed window.
7. The system of claim 3 wherein said halftone modulation control
comprises: reducing said energy directed on said print target by
dumping a portion of said energy directed on said target with a
beam dump wherein said portion of said energy directed on said
target corresponds with said present speed when said present speed
is in said halftone modulation control speed window.
8. The system of claim 1 wherein said print target comprises a
substrate and thermochromic ink.
9. A printing method comprising: moving a print target with a
transport system; directing energy on said print target with a
laser; and adjusting said energy directed on said print target
according to a present speed of said print target with a control
system.
10. The method of claim 9 wherein said control system further
comprises: an analog control; a scrolling window control; a pulse
width modulation control; and a halftone modulation control.
11. The method of claim 10 further comprising: implementing said
analog control when said present speed of said target is in an
analog control speed range; implementing said scrolling window
control when said present speed of said target is in a scrolling
window control speed range; implementing said pulse width control
when said present speed of said target is in a pulse width control
speed window; and implementing said halftone modulation control
when said present speed of said target is in a halftone modulation
control speed window.
12. The method of claim 11 wherein said analog control comprises:
providing an input current to a laser diode array wherein said
input current results in an output power of said laser diode that
has a substantially linear relationship to said input current.
13. The method of claim 11 wherein said scrolling window control
comprises: adjusting the exposure time said energy is directed on
said print target by adjusting a target window size associated with
said print target wherein said target window size corresponds with
said present speed when said present speed is in said scrolling
window control speed range.
14. The method of claim 11 wherein said pulse width modulation
control comprises: adjusting an exposure time said energy is
directed onto said print target wherein said exposure time
corresponds with said present speed when said present speed is in
said pulse width control speed window.
15. The method of claim 11 wherein said halftone modulation control
comprises: reducing said energy directed on said print target by
dumping a portion of said energy directed on said target with a
beam dump wherein said portion of said energy directed on said
target corresponds with said present speed when said present speed
is in said halftone modulation control speed window.
16. A printing apparatus comprising: a transport system configured
to move a print target; a laser for directing energy on said print
target; and a control system configured to adjust said energy
directed on said print target according to a present speed of said
print target said control system further comprising: implementing
an analog control when said present speed of said target is in an
analog control speed range; implementing a scrolling window control
when said present speed of said target is in a scrolling window
control speed range; implementing a pulse width control when said
present speed of said target is in a pulse width control speed
window; and implementing a halftone modulation control when said
present speed of said target is in a halftone modulation control
speed window.
17. The apparatus of claim 16 wherein said analog control
comprises: providing an input current to a laser diode array
wherein said input current results in an output power of said laser
diode that has a substantially linear relationship to said input
current.
18. The apparatus of claim 16 wherein said scrolling window control
comprises: adjusting the exposure time said energy is directed on
said print target by adjusting a target window size associated with
said print target wherein said target window size corresponds with
said present speed when said present speed is in said scrolling
window control speed range.
19. The apparatus of claim 16 wherein said pulse width modulation
control comprises: adjusting an exposure time said energy is
directed onto said print target wherein said exposure time
corresponds with said present speed when said present speed is in
said pulse width control speed window.
20. The apparatus of claim 16 wherein said halftone modulation
control comprises: reducing said energy directed on said print
target by dumping a portion of said energy directed on said target
with a beam dump wherein said portion of said energy directed on
said target corresponds with said present speed when said present
speed is in said halftone modulation control speed window.
Description
CROSS REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application claims the priority and benefit
under 35 U.S.C. .sctn. 119(e) of U.S. Provisional Patent
Application Ser. No. 62/382,412 filed Sep. 1, 2016, entitled
"MULTI-MODE LASER ENERGY CONTROL FOR THERMOCHROMIC PRINT SYSTEMS."
U.S. Provisional Patent Application Ser. No. 62/382,412 is herein
incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] Embodiments are generally related to the field of printing.
Embodiments are also related to methods and systems for
thermochromic printing. Embodiments are further related to methods
and systems for tracking media speed and controlling incident
energy accordingly. Embodiments are related to methods and systems
for implementing a control architecture that provides transitions
between control schemes for thermochromic printing according to
media speed.
BACKGROUND
[0003] New marking technology based on thermochromic inks are
becoming increasingly popular. Such marking technologies use
thermochromic ink based labels. Thermochromic ink based labels work
by permanently changing state according to the amount of energy
deposited over a given area. The technology provides an analog or
grayscale printing capability where pixels are developed after
exposure to some minimum threshold amount of energy deposited per
unit area. Complex systems are required for directing near
sufficient energy onto a moving media.
[0004] In prior art embodiments, fixed speed media paths are
required, or assumed, in order to ensure the correct amount of
energy is deposited in the correct portion of the label for the
thermochromic ink to be developed. However, fixed speeds are rarely
practical and in some cases, not possible in real world
applications. Prior art methods and systems are not equipped to
image media on a process line at speeds ranging from a standstill
up to 2 meters per second or faster. Retrofitting existing process
lines to operate at a fixed speed is expensive and in some cases
impossible.
[0005] For processing lines with variable speeds, prior art marking
techniques that assume fixed media speed provide poor quality
imaging. In addition, small variations in an otherwise constant
media speed, caused by process line errors or other such events,
can result in missed markings or failure to mark the desired area
at all. Poor quality markings and missed markings are expensive to
detect and correct, and can result in significant cost.
[0006] Accordingly, a need exists for print systems equipped to
track media speed and adjust the energy levels of the marking
engine to provide a consistent uniform energy at the media
surface.
SUMMARY
[0007] The following summary is provided to facilitate an
understanding of some of the innovative features unique to the
embodiments disclosed and is not intended to be a full description.
A full appreciation of the various aspects of the embodiments can
be gained by taking the entire specification, claims, drawings, and
abstract as a whole.
[0008] It is, therefore, one aspect of the disclosed embodiments to
provide a method and system for printing.
[0009] It is another aspect of the disclosed embodiments to provide
a method and system for thermochromic printing.
[0010] It is yet another aspect of the disclosed embodiments to
provide an enhanced method and system for controlling the energy
incident on media in a thermochromic printing system according to
media speed.
[0011] The aforementioned aspects and other objectives and
advantages can now be achieved as described herein. A printing
system, method, and apparatus comprises a transport system
configured to move a print target, a laser for directing energy on
the print target, and a control system configured to adjust the
energy directed on the print target according to a present speed of
the print target. In an embodiment, the control system further
comprises an analog control, a scrolling window control, a pulse
width modulation control, and a halftone modulation control. The
control system implements the analog control when the present speed
of the target is in an analog control speed range, the control
system implements the scrolling window control when the present
speed of the target is in a scrolling window control speed range,
the control system implements the pulse width control when the
present speed of the target is in a pulse width control speed
window, and the control system implements the halftone modulation
control when the present speed of the target is in a halftone
modulation control speed window.
BRIEF DESCRIPTION OF THE FIGURES
[0012] The accompanying figures, in which like reference numerals
refer to identical or functionally-similar elements throughout the
separate views and which are incorporated in and form a part of the
specification, further illustrate the embodiments and, together
with the detailed description, serve to explain the embodiments
disclosed herein.
[0013] FIG. 1 depicts a block diagram of a computer system which is
implemented n accordance with the disclosed embodiments;
[0014] FIG. 2 depicts a graphical representation of a network of
data-processing devices in which aspects of the present invention
may be implemented;
[0015] FIG. 3 depicts a computer software system for directing the
operation of the data-processing system depicted in FIG. 1, in
accordance with an example embodiment;
[0016] FIG. 4 depicts a block diagram of a printing system in
accordance with the disclosed embodiments;
[0017] FIG. 5 depicts a block diagram of a DLP mirror mapping in
accordance with the disclosed embodiments;
[0018] FIG. 6 depicts a chart illustrating an increase in energy by
flashing media in accordance with disclosed embodiments;
[0019] FIG. 7 depicts a flow chart illustrating logical operational
steps for controlling energy incident on media in accordance with
the disclosed embodiments;
[0020] FIG. 8 depicts a chart illustrating control regions as a
function of process transport speed in accordance with the
disclosed embodiments;
[0021] FIG. 9 depicts a chart illustrating power as a function of
current in accordance with the disclosed embodiments;
[0022] FIG. 10 depicts a chart illustrating groups of DLP mirror
rows as function of process speed in accordance with the disclosed
embodiments;
[0023] FIG. 11 depicts a chart illustrating on time as a function
of process speed in accordance with the disclosed embodiments;
[0024] FIG. 12 depicts a chart illustrating process timing
associated with mirror on time in accordance with the disclosed
embodiments;
[0025] FIG. 13 depicts a chart illustrating process timing
associated with active mirrors in accordance with the disclosed
embodiments;
[0026] FIG. 14 depicts a flow chart illustrating logical
operational steps for controlling energy in an analog control mode
in accordance with the disclosed embodiments;
[0027] FIG. 15 depicts a flow chart illustrating logical
operational steps for controlling energy in a scrolling window
control mode in accordance with the disclosed embodiments;
[0028] FIG. 16 depicts a flow chart illustrating logical
operational steps for controlling energy in a pulse width
modulation control mode in accordance with the disclosed
embodiments; and
[0029] FIG. 17 depicts a flow chart illustrating logical
operational steps for controlling energy in a halftoning control
mode in accordance with the disclosed embodiments.
DETAILED DESCRIPTION
[0030] The particular values and configurations discussed in these
non-limiting examples can be varied and are cited merely to
illustrate at least one embodiment and are not intended to limit
the scope thereof.
[0031] FIGS. 1-3 are provided as exemplary diagrams of
data-processing environments in which embodiments of the present
invention may be implemented. It should be appreciated that FIGS.
1-3 are only exemplary and are not intended to assert or imply any
limitation with regard to the environments in which aspects or
embodiments of the disclosed embodiments may be implemented. Many
modifications to the depicted environments may be made without
departing from the spirit and scope of the disclosed
embodiments.
[0032] A block diagram of a computer system 100 that executes
programming for implementing the methods and systems disclosed
herein is shown in FIG. 1. A general computing device in the form
of a computer 110 may include a processing unit 102, memory 104,
removable storage 112, and non-removable storage 114. Memory 104
may include volatile memory 106 and non-volatile memory 108.
Computer 110 may include or have access to a computing environment
that includes a variety of transitory and non-transitory
computer-readable media such as volatile memory 106 and
non-volatile memory 108, removable storage 112 and non-removable
storage 114. Computer storage includes, for example, random access
memory (RAM), read only memory (ROM), erasable programmable
read-only memory (EPROM) and electrically erasable programmable
read-only memory (EEPROM), flash memory or other memory
technologies, compact disc read-only memory (CD ROM), Digital
Versatile Disks (DVD) or other optical disk storage, magnetic
cassettes, magnetic tape, magnetic disk storage, or other magnetic
storage devices, or any other medium capable of storing
computer-readable instructions as well as data, including data
comprising frames of video.
[0033] Computer 110 may include or have access to a computing
environment that includes input 116, output 118, and a
communication connection 120. The computer may operate in a
networked environment using a communication connection to connect
to one or more remote computers or devices. The remote computer may
include a personal computer (PC), server, router, network PC, a
peer device or other common network node, or the like. The remote
device may include a sensor, photographic camera, video camera,
accelerometer, gyroscope, medical sensing device, tracking device,
or the like. The communication connection may include a Local Area
Network (LAN), a Wide Area Network (WAN), or other networks. This
functionality is described in more fully in the description
associated with FIG. 2 below.
[0034] Output 118 is most commonly provided as a computer monitor,
but may include any computer output device. Output 118 may also
include a data collection apparatus associated with computer system
100. In addition, input 116, which commonly includes a computer
keyboard and/or pointing device such as a computer mouse, computer
track pad, or the like, allows a user to select and instruct
computer system 100. A user interface can be provided using output
118 and input 116. Output 118 may function as a display for
displaying data and information for a user and for interactively
displaying a graphical user interface (GUI) 130.
[0035] Note that the term "GUI" generally refers to a type of
environment that represents programs, files, options, and so forth
by means of graphically displayed icons, menus, and dialog boxes on
a computer monitor screen. A user can interact with the GUI to
select and activate such options by directly touching the screen
and/or pointing and clicking with a user input device 116 such as,
for example, a pointing device such as a mouse and/or with a
keyboard. A particular item can function in the same manner to the
user in all applications because the GUI provides standard software
routines (e.g., module 125) to handle these elements and report the
user's actions. The GUI can further be used to display the
electronic service image frames as discussed below.
[0036] Computer-readable instructions, for example, program module
125, which can be representative of other modules described herein,
are stored on a computer-readable medium and are executable by the
processing unit 102 of computer 110. Program module 125 may include
a computer application. A hard drive, CD-ROM, RAM, Flash Memory,
and a USB drive are just some examples of articles including a
computer-readable medium.
[0037] FIG. 2 depicts a graphical representation of a network of
data-processing systems 200 in which aspects of the present
invention may be implemented. Network data-processing system 200 is
a network of computers in which embodiments of the present
invention may be implemented. Note that the system 200 can be
implemented in the context of a software module such as program
module 125. The system 200 includes a network 202 in communication
with one or more clients 210, 212, and 214. Network 202 is a medium
that can be used to provide communications links between various
devices and computers connected together within a networked data
processing system such as computer system 100. Network 202 may
include connections such as wired communication links, wireless
communication links, or fiber optic cables. Network 202 can further
communicate with one or more servers 206, one or more external
devices such as printer 204, and a memory storage unit such as, for
example, memory or database 208.
[0038] In the depicted example, printer 204 and server 206 connect
to network 202 along with storage unit 208. In addition, clients
210, 212, and 214 connect to network 202. These clients 210, 212,
and 214 may be, for example, personal computers or network
computers. Computer system 100 depicted in FIG. 1 can be, for
example, a client such as client 210, 212, and/or 214.
Alternatively, clients 210, 212, and 214 may also be, for example,
a photographic camera, video camera, tracking device, sensor,
accelerometer, gyroscope, medical sensor, etc.
[0039] Computer system 100 can also be implemented as a server such
as server 206, depending upon design considerations. In the
depicted example, server 206 provides data such as boot files,
operating system images, applications, and application updates to
clients 210, 212, and 214, and/or to printer 204. Clients 210, 212,
and 214 and printer 204 are clients to server 206 in this example.
Network data-processing system 200 may include additional servers,
clients, and other devices not shown. Specifically, clients may
connect to any member of a network of servers, which provide
equivalent content.
[0040] In the depicted example, network data-processing system 200
is the Internet with network 202 representing a worldwide
collection of networks and gateways that use the Transmission
Control Protocol/Internet Protocol (TCP/IP) suite of protocols to
communicate with one another. At the heart of the Internet is a
backbone of high-speed data communication lines between major nodes
or host computers consisting of thousands of commercial,
government, educational, and other computer systems that route data
and messages. Of course, network data-processing system 200 may
also be implemented as a number of different types of networks such
as, for example, an intranet, a local area network (LAN), or a wide
area network (WAN). FIGS. 1 and 2 are intended as examples and not
as architectural limitations for different embodiments of the
present invention.
[0041] FIG. 3 illustrates a computer software system 300, which may
be employed for directing the operation of the data-processing
systems such as computer system 100 depicted in FIG. 1. Software
application 305 may be stored in memory 104, on removable storage
112, or on non-removable storage 114 shown in FIG. 1, and generally
includes and/or is associated with a kernel or operating system 310
and a shell or interface 315. One or more application programs,
such as module(s) 125, may be "loaded" (i.e., transferred from
removable storage 112 into the memory 104) for execution by the
data-processing system 100. The data-processing system 100 can
receive user commands and data through user interface 315, which
can include input 116 and output 118, accessible by a user 320.
These inputs may then be acted upon by the computer system 100 in
accordance with instructions from operating system 310 and/or
software application 305 and any software module(s) 125
thereof.
[0042] Generally, program modules (e.g., module 125) can include,
but are not limited to, routines, subroutines, software
applications, programs, objects, components, data structures, etc.,
that perform particular tasks or implement particular abstract data
types and instructions. Moreover, those skilled in the art will
appreciate that the disclosed method and system may be practiced
with other computer system configurations such as, for example,
hand-held devices, multi-processor systems, data networks,
microprocessor-based or programmable consumer electronics,
networked personal computers, minicomputers, mainframe computers,
servers, and the like.
[0043] Note that the term module as utilized herein may refer to a
collection of routines and data structures that perform a
particular task or implements a particular abstract data type.
Modules may be composed of two parts: an interface, which lists the
constants, data types, variable, and routines that can be accessed
by other modules or routines; and an implementation, which is
typically private (accessible only to that module) and which
includes source code that actually implements the routines in the
module. The term module may also simply refer to an application
such as a computer program designed to assist in the performance of
a specific task such as word processing, accounting, inventory
management, etc.
[0044] The interface 315 (e.g., a graphical user interface 130) can
serve to display results, whereupon a user 320 may supply
additional inputs or terminate a particular session. In some
embodiments, operating system 310 and GUI 130 can be implemented in
the context of a "windows" system. It can be appreciated, of
course, that other types of systems are possible. For example,
rather than a traditional "windows" system, other operation systems
such as, for example, a real time operating system (RTOS) more
commonly employed in wireless systems may also be employed with
respect to operating system 310 and interface 315. The software
application 305 can include, for example, module(s) 125, which can
include instructions for carrying out steps or logical operations
such as those shown and described herein.
[0045] The following description is presented with respect to
embodiments of the present invention, which can be embodied in the
context of a data-processing system such as computer system 100, in
conjunction with program module 125, and data-processing system 200
and network 202 depicted in FIGS. 1-3. The present invention,
however, is not limited to any particular application or any
particular environment. Instead, those skilled in the art will find
that the system and method of the present invention may be
advantageously applied to a variety of system and application
software including database management systems, word processors,
and the like. Moreover, the present invention may be embodied on a
variety of different platforms including Macintosh, UNIX, LINUX,
and the like. Therefore, the descriptions of the exemplary
embodiments, which follow, are for purposes of illustration and not
considered a limitation.
[0046] One embodiment comprises a new marking technology based on
thermochromic inks. The embodiment uses thermochromic ink based
labels which permanently change state depending on the amount of
energy deposited over a given area. The marking subsystem can use a
combination of high power Laser Diode Arrays (LDAs) in conjunction
with Digital Light Projection (DLP) mirror arrays to direct near
infrared energy onto a moving media.
[0047] The embodiments disclosed herein are configured to image
media from a standstill up to 2 meters per second, or faster in
some cases. In the simplest terms, the marking subsystem can track
the media speed and adjust the energy levels incident on the media
to provide a consistent uniform energy at the media surface.
[0048] One potential complexity arises because an LDA may not
output sufficient energy in a "line time". A "line time" is
analogous to a scanline in traditional ROS based laser printers. As
such embodiments disclosed herein use a scrolling window to repeat
the data for a given area as it moves across the marking window.
The combination of subsystem constraints requires a multi-mode
imaging system that can track media speeds and adjust laser energy
from standstill up through a range of media speeds.
[0049] FIG. 4 illustrates a high-level block diagram of the major
components in a printing system 400 in accordance with one
embodiment. The media 405 (a package in this exemplary embodiment)
is transported via a transport system 410, such as a conveyor belt.
Other such mechanisms for transporting media may also be used. In
other embodiments, the system may not include a transport system
410 at all. In such an embodiment, the media would not move.
[0050] The media 405 includes a blank thermochromic ink label 415
attached to its exterior surface. As the media 405 moves along the
conveyor belt 410, it trips the product lead edge sensor 420 which
informs the image input system 425 that a target, such as label 415
is in position for marking.
[0051] An encoder 430, attached to the transport system 410,
provides one pulse or tick for every line of movement. A line
corresponds to one pixel width line of marking. In this example, a
line is defined as 1/274 of an inch. In other embodiments, a line
may be defined as any size, according to design requirements. The
image input system 425 transmits a line of data to the digital
micro mirror device (DMD) board 435. The DMD board 435 in turn
processes the line of data and loads it into the DLP mirror array
buffer.
[0052] At the next encoder tick, the DMD hardware provides a DLP
load signal which causes the data previously loaded in the DLP
mirror array buffer to drive the DLP mirrors 440 to a required
position. This processing time is known as the mirror settling time
and is generally on the order of 12 microseconds. The DLP mirrors
440 direct the LDA light 445 to either a beam dump area (not
shown), absorptive material in the optics path, or to the optics
path 450 and eventually onto the media 405.
[0053] The thermochromic ink label 415 material can use a "write
black" system meaning energy must be directed onto the label in
order to create a visible pixel. Most commonly the energy directed
onto the thermochromic ink label 415 is laser energy, but other
forms of energy may alternatively be used.
[0054] In an embodiment, two LDAs, LDA 455 and LDA 456 are used to
generate sufficient energy at the media 405. In other embodiments,
different numbers of LDAs may also be used depending on design
considerations. A number of lenses and mirrors in addition to the
DLP mirrors 440 may be required to adequately provide energy to the
thermochromic ink. However, all such optical elements contribute to
energy losses.
[0055] The optical beam path 460 takes the laser beam from each of
the LDAs including LDA 455 and LDA 456 and creates a uniform 20
rectangular shaped "beam". The beam is reflected off the DLP mirror
array 440 to create a 20 pixel map. The optics system ensures that
image data is focused at the correct point in the marking zone 465.
The marking zone 465 represents the area where the beam is incident
on the thermochromic ink label 415. In the exemplary situation
illustrated in FIG. 4, the thermochromic ink label 415 has passed
the marking zone 465.
[0056] A preheat subsystem, consisting of an LDA 470 and optics
475, directs energy to the media in an area adjacent to, and just
preceding, the marking zone 465 called the preheat zone 480. The
preheat function brings the thermochromic ink label 415 to a
temperature point just below the point at which the thermochromic
ink label 415 will begin to expose and reveal visible marking.
[0057] The process of transmitting image data, one line per encoder
430 tick/pulse, to the DLP mirrors 440 repeats as the package moves
on the transport system 410. The imaging input system 425 has
internal timing logic to control when the image data or blanking
data is passed to the marking zone 465. As the trail edge of the
media 405 passes by the sensor 420, a signal is generated informing
the imaging input system 425 that printing is complete. The imaging
input system 425 can then output blank data until the next media
arrives at the sensor 420.
[0058] FIG. 5 illustrates a DLP mirror mapping 500 in an exemplary
embodiment of the systems and methods disclosed herein. It should
be understood that the number of mirrors and associated sizes are
exemplary and provided for illustrative purposes only. Other
numbers and sizes may alternatively be used without departing from
the scope of this disclosure.
[0059] In the present embodiments, laser energy is directed by the
DLP mirror array to one of two locations, a beam dump area or a
precise 2D point in the marking zone. In an exemplary embodiment,
the DLP can consist of a matrix of 1024 columns of mirrors and 768
mirror rows as illustrated in FIG. 5. The printer system uses a
subset of the total number of mirrors--1024.times.480. This
corresponds to 491,000 mirrors.
[0060] The optical system takes the 1024 columns and translates
them to 1/960 inch per mirror in the cross-process or X dimension.
Similarly, in the process or V dimension 60 mirror rows are grouped
and correspond to 1/274 of an inch. FIG. 5 shows the DLP, active
image area (where the 2D beam impinges the DLP), the 8 groups or
lines, and the 60 mirror rows that make up each line.
[0061] Given this mapping, the amount of energy that can be
directed to a spot or pixel on the media in a line time is
insufficient to cause the label material to fully develop an
Optical Density (OD) of 1 or more. Thus, in order to direct more
energy on a pixel, a line of image data can be repeated N line
times. The media moves a line width every encoder tick. Thus, the
image data can be moved by the same amount to "reimage" or
"reflash" a line. This process can be repeated N times to increase
the energy deposited on a pixel and hence increase the OD. In an
exemplary embodiment, 8 line times are required to create a pixel
with an OD greater than one. Thus, each line of data is shifted 60
mirror rows every encoder tick.
[0062] FIG. 6 illustrates the general concept of increasing the
energy deposited on a pixel through a scrolling window that flashes
the same line of data multiple times in plot 605. The plot 600
shows a fixed point on the media flashed 8 times. The plot 600
illustrates that each flash increases the cumulative energy at the
fixed point until the maximum threshold energy is reached. The
concept of preheating is also illustrated in plot 600. As shown,
preheating can also be incorporated before the media is flashed so
that the media is heated to just below the minimal threshold energy
required for visible optical density.
[0063] It should be appreciated that when the encoder pulse
frequency varies, the transport speed of the media is fluctuating.
The fluctuating speed of the media can result in significant over
or under exposure of the thermochromic ink. For example, if the
media speed slows during the exposure window, the corresponding
line time goes up, which could result in a significant overexposure
of the thermochromic ink. Similarly, if the media speed increases
the line time decreases and the thermochromic irk may be
dramatically underexposed. Thus, it is a critical aspect of the
embodiments disclosed herein that the marking system 400 track and
adjust the intensity of the LDA to ensure operation from a
standstill up to the maximum defined speed.
[0064] In an embodiment, a multi-mode energy control method can be
used to allow the media in a thermochromic printing system to vary
from a standstill to a predetermined maximum speed. The energy
control method ensures that the print system provides the desired
amount of energy on the media regardless of speed or speed changes,
and that the print system does not generate image artifacts due to
media speed changes. The embodiments employ a multi-mode energy
control system and method with four operating regions, an analog
control region, a scrolling window control region, a pulse width
modulation control region, and a halftoning control region.
[0065] In an embodiment, the image input system 425 implements the
primary control loop associated with the energy control method
disclosed herein. FIG. 7 illustrates a flow chart 700 of logical
operational steps associated with the primary control loop
implemented by the image input system 425. The control loop starts
at block 705. At block 710, the image input system 425 receives the
encoder input tick or pulse. The image input system 425 then
calculates the transport system speed as well the rate of change in
the transport system speed, as shown at block 715. The image input
system 425 then determines what control region and associated
control mode is appropriate according to the current speed, as
shown at block 720. The image input system 425 then implements the
control mode by adjusting the various actuators based on the
required operating mode, as shown at block 725. The process then
recycles. The control loop ends 730 when printing is complete.
[0066] Thus, as illustrated in flow chart 700, the image input
system 425 continuously monitors the transport encoder speed. A
dynamic tracking module can track the encoder period (1/speed)
using a sliding window. The sliding window has an upper period and
lower period register along with a window increment. The image
input system 425 control loop is used to monitor this period and
take appropriate action to adjust control mode.
[0067] FIG. 8 illustrates a plot 800 of transport process speed
versus laser power. The plot illustrates an exemplary case where
the goal is to maintain a constant energy of 110 mW/mm2,
independent of the transport system speed. It should be appreciated
that 110 mW/mm2 is an example energy level. Actual values will vary
based on media characteristics, optical losses, LDA operating
regions, etc.
[0068] Plot 800 illustrates the control modes used at various
process speeds to maintain constant energy incident on the media.
For example, if the transport speed S.sub.i of sample i is in the
range of S.sub.Analog 807.ltoreq.S.sub.i.ltoreq.S.sub.Max 806, the
system is in Analog control region 805. If the transport speed
S.sub.i is in the range of S.sub.Swm
811.ltoreq.S.sub.i.ltoreq.S.sub.Analog 807, the system is in the
scrolling window control region 810. If the transport speed S.sub.i
is in the range of S.sub.Pwm 816.ltoreq.S.sub.i.ltoreq.S.sub.Swm
811, the system is in the pulse width modulation control region
815. And if the transport speed S.sub.i is in the range of Zero
821.ltoreq.S.sub.i.ltoreq.S.sub.Pwm 816, the system is in the
Halftoning control region 820. Note S.sub.Analog 807, S.sub.Max
806, S.sub.Swm 811, and S.sub.Pwm 816 can be empirically measured
and stored in the image input system 425 and provided as inputs to
the multi mode energy control loop.
[0069] For certain, generally higher process speeds where
S.sub.Analog 807.ltoreq.S.sub.i.ltoreq.S.sub.Max 806, an analog
control mode is employed. Laser diode arrays have a range in which
their output power level is a linear function of their input
current. Below a certain value, typically 30-40% of full power, the
power across the LDAs becomes non-uniform. This can lead to image
artifacts depending on the level of non-uniformity. FIG. 9
illustrates a plot 900 that shows the input current as a percentage
of full scale and the corresponding Irradiance output. The analog
control mode is thus selected when the incident irradiance stays in
the linear region of the Irr curve. The LDA analog current is given
as ISET. This region is defined at the beginning as ISET.sub.min
905 and ends at ISET.sub.max 910. In the analog control region 805,
the image input system 425 controls LDA power by varying ISET
within the linear range. In the exemplary plot 900, the ISET varies
between 25% and 90% of full-scale. The control loop remains in the
analog control mode until process speed dips below S.sub.Analog
807. At this point the control loop moves t the scrolling window
control mode.
[0070] In the scrolling window control region 810 of S.sub.Swm
811<S.sub.i.ltoreq.S.sub.Analog 807, analog control remains but
is supplemented by reducing the scrolling window width. Reducing
the scrolling window width reduces power in order to stay on the
constant energy curve. The scrolling window control region 810 is a
hybrid mode that both adjusts ISET in a narrow range and modulates
the scroll window size. The ISET value, shown in plot 1000 in FIG.
10, is increased to the point where irradiance corresponding to
ISET with 7 scrolling lines and is equal to the irradiance
corresponding to ISET.sub.min with 8 scrolling lines. At this point
the scrolling window is reduced from 8 to 7.
[0071] As the transport system speed decreases or continues to
decelerate, the Analog irradiance control continues until
ISET=ISET.sub.min. At this point the scrolling window size is
reduced again 7-1=6. ISET is increased back to an irradiance
corresponding to ISET with 7 scrolling lines. This process
continues as transport system speed decreases until the scrolling
window size is one and ISET.sub.min is reached. The transport speed
is now equal to S.sub.Pwm 811 and scrolling window mode is no
longer capable of reducing the irradiance. Thus, ISET remains at
ISET.sub.min and the multi mode energy control loop moves to the
pulse width modulation region 815.
[0072] In the pulse width modulation region 815, the transport
system speed, S.sub.i, is in the range of S.sub.Pwm
811.ltoreq.S.sub.i<816. In pulse width modulation region 815,
the scrolling window is set to 1 and the LDA analog current, ISET,
is set to ISET.sub.min. FIG. 11 includes a plot 1100 of process
speed and pulse width modulation "Time On."
[0073] In the pulse width modulation region the multi-mode energy
control loop actuator is the time duration of an image. In the
pulse width modulation region, the pixel "on time" is modulated as
a function of process speed. For example, the pixel on time can be
shortened to effectively reduce the energy incident on the media.
Even with such modulation of the pixel on time, eventually a limit
is reached. This limit is defined as the minimum time that DLP can
be on. Experimentally, this limit has been observed to be on the
order to 10 .mu.seconds, but the limit may vary depending on design
constraints. Note the total cycle time is 44 .mu.seconds.
[0074] The final limiting, parameter in the pulse width modulation
region is the amount of time required to load DLP array groups. In
an exemplary embodiment, this includes loading 2 DLP array groups
and 96 DLP mirror rows of which 60 are active. In such a scenario
approximately 10 .mu.seconds are required to load 2 groups (i.e.,
load pixels). Approximately 12 .mu.seconds are required for the
mirrors to settle to the desired state. Approximately 10
.mu.seconds are needed to load a group (i.e., load the off state to
both groups). Note that the DLP stays in the previous state while
the new off state is loaded. Approximately 12 .mu.seconds are
required for all the mirrors to settle to the off state. This
equates to approximately 44 .mu.seconds of total cycle time with an
active time of approximately 10 .mu.seconds. It is once again
important to note that this scenario is exemplary and the timing
may differ depending on design constrains and choices.
[0075] FIG. 12 illustrates a chart 1200 that shows how the on time
varies as a function of a few exemplary transport speed values.
Process speeds in the pulse width modulation region require the
image input system 425 to send both a line of image data and, after
a variable amount of time, send a blank line of image data. In
other embodiments, the DMD may also provide a self-timed mode where
the image line includes metadata defining the amount of time to
leave the data on.
[0076] The halftone region 820 is entered when the transport system
speed, S.sub.i, is in the range of zero
821.ltoreq.S.sub.i<S.sub.Pwm 816. At the point where
S.sub.i=S.sub.Pwm, the scrolling window is set to 1, the LDA
current is set to ISET.sub.min, and the DLP on time is set to a
minimum (for example, approximately 10 .mu.seconds in the above
example). To further reduce the irradiance at the media, the multi
mode energy control loop can reduce energy incident on the media by
systematically turning off a subset of the DLP mirrors until only
one mirror remains on.
[0077] Continuing with the exemplary embodiment with transport
speeds<S.sub.Pwm 816, the 60 mirrors that represent 1/960'' are
modulated to reduce irradiance. At these slow speeds, grayscale
printing will revert to binary printing as the system reduces
energy levels by turning off mirrors. FIG. 13 provides a chart 1300
which shows the exemplary case where the transport speed is 0.0016
M/s and all 60 mirrors are on. As the speed is further reduced by a
factor of two, the number of mirrors turned on drops to 30. At
0.00001 M/s, the system will reach its limit with only 1 mirror
being on.
[0078] FIGS. 14-17 illustrate the control procedure for each of the
analog control mode, scrolling window control mode, pulse width
modulation control mode, and halftone modulation control mode ire
accordance with the disclosed embodiments.
[0079] FIG. 14 illustrates the control procedure 1400 associated
with an analog control mode. At step 1405, the encoder input is
provided to the image input system 425. The image input system 425
implements the control loop method 700, and upon determining the
process speed is within the speed range for the application of the
analog control sets the ISET at the necessary value between, for
example, 25% and 90% of full strength at step 1410. A constant
current source is provided to one or more LDAs at step 1415 which
produce one or more laser beams. The optical beam path combines
beams at step 1420 and focuses them on the DLP. The resulting beams
from the DLP are directed via the optical beam path to the media at
step 1425. Note that as described above, the beams may be directed
onto the media in flashes so that the total energy on the media is
sufficient to make the desired portions of the thermochromic ink
visible.
[0080] FIG. 15 illustrates the control procedure 1500 associated
with a scrolling window control mode. At step 1505, the encoder
input is provided to the image input system 425. The image input
system 425 implements the control loop method 700, and upon
determining the process speed is within the speed range for the
Application of the scrolling window control mode sets the ISET at
the necessary value between, for example 25% and 32% of full
strength at step 1510. A constant current source is provided to one
or more LDAs which produce one or more laser beams at step 1515.
The optical beam path combines beams at step 1520 and focuses them
on the DLP. In the scrolling window control mode, the ISET is still
adjusted as in the analog control mode, but the scroll window size
is also modulated to reduce the incident energy on the media. The
resulting beams from the DLP are directed via the optical beam path
to the media at step 1525.
[0081] FIG. 16 illustrates the control procedure 1600 associated
with a pulse width modulation control mode. At step 1605, the
encoder input is provided to the image input system 425. The image
input system 425 implements the control loop method 700, and upon
determining the process speed is within the speed range for the
Application of the pulse width modulation control mode sets the
ISET at the necessary value of, for example, 25% at step 1610. A
constant current source is provided to one or more LDAs which
produce one or more laser beams at step 1615. The optical beam path
combines beams at step 1620 and focuses them on the DLP. In the
pulse width modulation control mode, the ISET is constant and the
scroll window size has been reduced to its minimum value. In
addition, the incident energy is further reduced by modulating the
pixel on time as a function of process speed. The resulting beams
from the DLP are directed via the optical beam path to the media at
step 1625.
[0082] FIG. 17 illustrates the control procedure 1700 associated
with a halftone modulation control mode. At step 1705, the encoder
input is provided to the image input system 425. The image input
system 425 implements the control loop method 700, and upon
determining the process speed is within the speed range for the
Application of the halftone control mode sets the ISET at the
necessary value of, for example, 25% at step 1710. A constant
current source is provided to one or more LDAs at step 1715 which
produce one or more laser beams. The optical beam path combines
beams at step 1720 and focuses them on the DLP. In the halftone
control mode, the ISET is constant, the scroll window size has been
reduced to its minimum value, and the on time of the beams is at a
minimum. In addition, DLP is further reduced by turning off mirrors
in the DLP as a function of transport speed. The resulting beams
from the mirrors in the DLP that are left on are directed via the
optical beam path to the media at step 1725.
[0083] At some speed, S.sub.NL, that can be empirically determined,
the response of the label material and resulting OD will become
non-linear. The multi mode energy control loop can compensate for
such non-linearities by adjusting any of the available actuators in
the operating zone.
[0084] In certain, embodiments, preheating can be accomplished by
directing a separate beam of laser light to the region just before
the marking zone in the preheating zone as shown in FIG. 4. The
preheat beam may have digital energy control (i.e., no DLP is in
the beam path) or may have only analog control. The preheat
function is used to bring the media up to a temperature just below
the minimum OD that is visible. This reduces the LDA energy
required to image a pixel via the DLP.
[0085] At very slow speeds the energy levels from the preheat step
may exceed the limit of invisibility, and create a gray or black
background image on the media. The multi-mode energy control loop
can use the transport system speed to determine if and when the
preheat is necessary. At transport system speeds where the preheat
step is off, the overall image path energy levels may need to be
increased to ensure an OD of >1 is achievable. The multi-mode
energy control loop can compensate for the higher energy levels by
varying which actuators are used for a given speed.
[0086] Based on the foregoing, it can be appreciated that a number
of embodiments, preferred and alternative, are disclosed herein.
For example, in one embodiment, a printing system comprises a
transport system configured to move a print target, a laser for
directing energy on the print target, and a control system
configured to adjust the energy directed on the print target
according to a present speed of the print target. In an embodiment,
the control system further comprises an analog control, a scrolling
window control, a pulse width modulation control, and a halftone
modulation control.
[0087] In another embodiment, the control system implements the
analog control when the present speed of the target is in an analog
control speed range, the control system implements the scrolling
window control when the present speed of the target is in a
scrolling window control speed range, the control system implements
the pulse width control when the present speed of the target is in
a pulse width control speed window, and the control system
implements the halftone modulation control when the present speed
of the target is in a halftone modulation control speed window.
[0088] In an embodiment, the analog control comprises providing an
input current to a laser diode array wherein the input current
results in an output power of the laser diode that has a
substantially linear relationship to the input current.
[0089] In an embodiment, the scrolling window control comprises
adjusting the exposure time the energy is directed on the print
target by adjusting a target window size associated with the print
target wherein the target window size corresponds with the present
speed when the present speed is in the scrolling window control
speed range.
[0090] In an embodiment, the pulse width modulation control
comprises adjusting an exposure time the energy is directed onto
the print target wherein the exposure time corresponds with the
present speed when the present speed is in the pulse width control
speed window.
[0091] In an embodiment, the halftone modulation control comprises
reducing the energy directed on the print target by dumping a
portion of the energy directed on the target with a beam dump
wherein the portion of the energy directed on the target
corresponds with the present speed when the present speed is in the
halftone modulation control speed window.
[0092] In an embodiment, the print target comprises a substrate and
thermochromic ink.
[0093] In an embodiment, a printing method comprises moving a print
target with a transport system, directing energy on the print
target with a laser, and adjusting the energy directed on the print
target according to a present speed of the print target with a
control system. The control system further comprises an analog
control, a scrolling window control, a pulse width modulation
control, and a halftone modulation control.
[0094] In an embodiment, the method further comprises implementing
the analog control when the present speed of the target is in an
analog control speed range; implementing the scrolling window
control when the present speed of the target is in a scrolling
window control speed range; implementing the pulse width control
when the present speed of the target is in a pulse width control
speed window; and implementing the halftone modulation control when
the present speed of the target is in a halftone modulation control
speed window.
[0095] In an embodiment, the analog control comprises providing an
input current to a laser diode array wherein the input current
results in an output power of the laser diode that has a
substantially linear relationship to the input current.
[0096] In an embodiment, the scrolling window control comprises
adjusting the exposure time the energy is directed on the print
target by adjusting a target window size associated with the print
target wherein the target window size corresponds with the present
speed when the present speed is in the scrolling window control
speed range.
[0097] In an embodiment, the pulse width modulation control
comprises adjusting an exposure time the energy is directed onto
the print target wherein the exposure time corresponds with the
present speed when the present speed is in the pulse width control
speed window.
[0098] In an embodiment, the halftone modulation control comprises
reducing the energy directed on the print target by dumping a
portion of the energy directed on the target with a beam dump
wherein the portion of the energy directed on the target
corresponds with the present speed when the present speed is in the
halftone modulation control speed window.
[0099] In yet another embodiment, a printing apparatus comprises a
transport system configured to move a print target; a laser for
directing energy on the print target; and a control system
configured to adjust the energy directed on the print target
according to a present speed of the print target the control system
further comprising: implementing an analog control when the present
speed of the target is in an analog control speed range,
implementing a scrolling window control when the present speed of
the target is in a scrolling window control speed range,
implementing a pulse width control when the present speed of the
target is in a pulse width control speed window, and implementing a
halftone modulation control when the present speed of the target is
in a halftone modulation control speed window.
[0100] In an embodiment, the analog control comprises providing an
input current to a laser diode array wherein the input current
results in an output power of the laser diode that has a
substantially linear relationship to the input current.
[0101] In an embodiment, the scrolling window control comprises
adjusting the exposure time the energy is directed on the print
target by adjusting a target window size associated with the print
target wherein the target window size corresponds with the present
speed when the present speed is in the scrolling window control
speed range.
[0102] In an embodiment, the pulse width modulation control
comprises adjusting an exposure time the energy is directed onto
the print target wherein the exposure time corresponds with the
present speed when the present speed is in the pulse width control
speed window.
[0103] In an embodiment, the halftone modulation control comprises
reducing the energy directed on the print target by dumping a
portion of the energy directed on the target with a beam dump
wherein the portion of the energy directed on the target
corresponds with the present speed when the present speed is in the
halftone modulation control speed window.
[0104] It will be appreciated that variations of the
above-disclosed and other features and functions, or alternatives
thereof, may be desirably combined into many other different
systems or applications. Also, that various presently unforeseen or
unanticipated alternatives, modifications, variations or
improvements therein may be subsequently made by those spilled in
the art which are also intended to be encompassed by the following
claims.
* * * * *